MathDB

p1. Sometimes one finds in an old park a tetrahedral pile of cannon balls, that is, a pile each layer of which is a tightly packed triangular layer of balls. A. How many cannon balls are in a tetrahedral pile of cannon balls of

N

layers? B. How high is a tetrahedral pile of cannon balls of

N

layers? (Assume each cannon ball is a sphere of radius

R

.)
p2. A prime is an integer greater than

1

whose only positive integer divisors are itself and

1

. A. Find a triple of primes

(p, q, r)

such that

p = q + 2

and

q = r + 2

. B. Prove that there is only one triple

(p, q, r)

of primes such that

p = q + 2

and

q = r + 2

.
p3. The function

g

is defined recursively on the positive integers by

g(1) =1

, and for

n>1

g(n)= 1+g(n-g(n-1))

. A. Find

g(1)

g(2)

g(3)

and

g(4)

. B. Describe the pattern formed by the entire sequence

g(1) , g(2 ), g(3), ...

C. Prove your answer to Part B.
p4. Let

x

y

and

z

be real numbers such that

x + y + z = 1

and

xyz = 3

. A. Prove that none of

x

y

, nor

z

can equal

1

. B. Determine all values of

x

that can occur in a simultaneous solution to these two equations (where

x , y , z

are real numbers).
p5. A round robin tournament was played among thirteen teams. Each team played every other team exactly once. At the conclusion of the tournament, it happened that each team had won six games and lost six games. A. How many games were played in this tournament? B. Define a circular triangle in a round robin tournament to be a set of three different teams in which none of the three teams beat both of the other two teams. How many circular triangles are there in this tournament? C. Prove your answer to Part B.
PS. You should use hide for answers. Collected [url=https://artofproblemsolving.com/community/c5h2760506p24143309]here.

Problem Statement